The advantages of mounting a power steering gear unit on the axle of a vehicle have been known to those active in the field for several years. With the power steering unit mounted on the axle, the steering linkages do not have to accommodate relative movement between the wheels and the frame. As the vehicle negotiates bumps in the road, the power steering unit simply moves as an integral part of the entire steering linkage system carried by the axle. The constant change in angle of the drag link and the consequent changing of steering forces that previously have been dealt with are now eliminated giving a definite edge in operability efficiency and ease of maintenance.
With dual steering, the advantages of axle mounting are even more prevalent. In a dual axle mounted system, the chance of dual force mismatch or "fighting" is eliminated. Axle mounting will provide greater incentive for vehical manufacturers, especially of large trucks, to move to dual steering.
Recent years has brought to the industry the reliable extensible and flexible connection between the steering shaft and the input shaft of the power steering unit. This development further opens the door to axle mounting on vehicles and has provided an impetus to develop a truly efficient dual steering.
At the present time, the need for added improvement in the system lies in the manner of mounting and locking the steering gear on the axle. The locking is critical since the reaction and shock forces between the steering gear and the axle are substantial, especially in large vehicles, such as heavy duty trucks, and all chance of movement or looseness must be eliminated.
My previous basic concept for AXLE MOUNTING OF INTEGRAL POWER STEERING GEAR, U.S. Pat. No. 3,970,166, issued July 20, 1976, taught the art the use of an integral locating pin and set screws and/or additional strategically located pins to resist the forces of reaction by providing direct and positive accommodation, both in the lateral, as well as the pivotal, directions. This successful axle mounting of an integral power steering gear included the concept of having the manufacturer ream a specially sized hole in the axle to receive a locating pin. This pin is designed to have a locational interference fit with the hole and thus holds the steering gear against any lateral movement.
My prior invention has been accepted in the industry as a great improvement over the previous locking arrangements wherein the forces of reaction of the steering gear unit are transmitted fully through the U-bolts with the U-bolts tending to develop looseness and eventually potential failure.
Because the manufacturer was required to provide a precision reamed hole in the axle, additional manufacturing costs are encountered. A savings, especially where the savings is in the area of eliminating the need for precision work can be substantial in terms of overall production of vehicles, such as trucks.
Furthermore I have discovered that in the process of installation, there is room for improved results in assembling the parts of the workers since the task of assembling interference fit parts is sometimes tedious and thus time consuming. My reasoning led me to the conclusion that a locating pin that is adjustable over a range of hole sizes would not only do away with the requirement for a precision reamed hole, but could greatly improve the installation process by the manufacturer. Another clear advantage that naturally follows would be that several different size pins for different makes and models of axles would not be required since one size adjustable pin would fit a wide range.